| Abstract/Contents: | "Tropical soda apple (TSA) has become a pernicious weed of pasturelands, vegetable crops, row crops, forestlands, and urban and natural areas in the southeastern United States. Since its introduction into Florida in the early 1980's TSA has spread into Alabama, Georgia, Louisiana, Mississippi, North Carolina, Pennsylvania, South Carolina, Tennessee, and Puerto Rico. TSA spead is attributed to livestock movement and contaminated composted manure and grass seeds from previously infested areas. Because TSA is classified as a tropical perennial, research was needed to determine survival potential in areas north of Florida. Experiments were established in a containment area near Stoneville, MS (latitude 33° 25'N) to determine the overwintering survival potential of TSA seeds (Experiment 1) and determine the growth, reproductive potential, and overwintering potential of mature TSA plants (Experiment 2). Experiment 1: Seeds were placed in nylon mesh bags and sealed with hot glue. On the first Monday in November in 1995, 1996, and 1997, bags containing seeds and intact fruit were placed 1 m above the soil surface, on the soil surface, or buried in a sandy loam soil at depths of 5, 10, and 15 cm. Bags of seed and fruit were retrieved the first Monday of April in 1995, 1996, and 1997. From each sample, three 100 seed samples were placed on a sandy loam soil, covered lightly with soil, and allowed to germinate in trays in the greenhouse at Stoneville, MS. Trays were watered from beneath to prevent soil disturbance. Emerged plants were counted and removed weekly until TSA plant emergence caused (ca. 6 wk period each year). Data were averaged over years and 14, 10, 48, 42, and 13% TSA plants emerged from 100, 0, -5, -10, and -15 cm, respectively from seed bags, while 86, 83, 48, 41, and 18% emerged from seed within fruit 100, 0, -5, -10, -15 cm respectively. Intact TSA fruit enhances the viability of overwintering TSA seeds above the soil surface, but viability was equivalent to seed alone at or below the soil surface because fruit shell degradation occurred during the winter. Experiment 2: TSA plants were raised in the greenhouse in 10 cm daim pots. Plants 10-15 cm tall were transplanted in the field in rows 2 m apart in mid April of 1995, 1996, and 1997. Plant height, length along the row, width across the row, number of fruits, and total plant weight (including fruit) were recorded in late October each year from 6 TSA plants. Fruit over 2.5 cm diam (before turning yellow) were counted, removed, and weihgted from all plants at biweekly intervals during the summer to prevent escape. TSA plant heights were 82, 64, and 72 cm; plant lengths were 237, 173, and 203 cm; plant widths were 275, 163, and 189 cm; plant weights were 9.9, 9.5 and 4.9 kg; and number of fruit were 119, 187, and 128 for 1996, 1997, and 1998, respectively. Plant weights were less in 1998 due to a hotter and dryer than normal summer and because most of the fruit were set and were smaller at the time of harvest. The number of TSA plants emerging the following year were recorded at biweekly intervals starting in May until mid June when the area was sprayed with glyphosate and disked repeatedly. No TSA plants emerged from rootstocks of the previous year in 1996 and 1997, but 83% if TSA plants survived the winter of 1997-1998. The winter of 1997-1998 was warmer than the other two winters (1995-1996 and 1996-1997) and warmer than normal for Stoneville, MS. From data in these two experiments, TSA seeds survived each year and TSA plants in one of three year were able to survive winter condition near Stoneville, MS. It is apparent that TSA plants have the ability to survive warmer than normal winters at or bellow latitude 33°N and that TSA will persist as an annual in areas where it cannot survive winters as a perennial." |
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